2.4.4 Frame Type

A frame is a rectangle on the screen that contains one or more Emacs windows. A frame initially contains a single main window (plus perhaps a minibuffer window) which you can subdivide vertically or horizontally into smaller windows.

Frames have no read syntax. They print in hash notation, giving the frame's title, plus its address in core (useful to identify the frame uniquely).

(selected-frame) => #<frame emacs@psilocin.gnu.org 0xdac80>

See section 29. Frames, for a description of the functions that work on frames.